1. Field of the Invention
The present invention relates to a projection TV, and more particularly, to an apparatus and a method of re-adjusting convergence of a projection TV.
2. Discussion of the Related Art
In general, there are many ways to correct the convergence of a projection TV having red/green/blue (R/G/B) projection tubes. FIG. 1 illustrates an example of typical convergence correction devices for a projection TV. The device shown in FIG. 1 includes R/G/B projection tubes 18r, 18g, and 18b; a screen 11; location detectors 12 placed on each side of the screen 11; a pattern generator 15 generating an alignment pattern; a signal switch/amplifier 16; and a convergence compensator 14 controlling convergence yokes 17r, 17g, and 17g in accordance with signals outputted from the location detectors 12. Each location detector 12 may include a phototransistor or a charged couple device (CCD) linear sensor for location detection.
A method of adjusting the convergence of a projection TV using the device shown in FIG. 1 will now be described in detail. First, the locations of the location detectors 12 placed on each side of the screen 11 are obtained using the signals outputted from the detectors 12. Next, a convergence error is calculated using the locations of the location detectors 12. Then the convergence is corrected based on the calculated convergence error value. However, the measured locations of the location detectors 12 are not precise enough due to many problems. For that reason, the convergence correction performance based on the above method is often unsatisfactory.
In order to solve at least the problems set above, a greater number of photo transistors or very expensive CCD linear sensors have been used, however, these create further problems of adding complexity to the system and increasing the production cost. Alternatively, amorphous solar cells are often used for precisely measuring the locations of the detectors, but they require supplemental devices such as an A/D converter and involve a complex algorithm for calculating the convergence error value.